How do glasses help us see? - Andrew Bastawrous and Clare Gilbert

譯者: Crystal Yip 審譯者: Max Chern

Almost 2000 years ago,

差不多二千年前

the Roman philosopher Seneca peered at his book through a glass of water.

羅馬哲學家塞內卡 透過一杯水來看他的書

Suddenly, the text below was transformed.

突然，杯下的文字改變了

The words magically became clear.

文字神奇地變得清晰

But it wasn't until a millennium later that that same principle

但直至一千年後，這一原理

would be used to create the earliest glasses.

會用以製作最早的眼鏡

Today, glasses can help millions of people with poor vision

今天，眼鏡幫助數百萬人 因未矯正「屈光不正」所致的視力不良

due to uncorrected refractive errors.

The key to understanding what that means lies with the term refraction,

要理解背後意義，關鍵在於「折射」──

the ability of a transparent medium, like glass,

光通過一種透明介質，例如玻璃、水 或眼睛時，介質改變光行進方向的能力

water,

or the eye to change the direction of light passing through it.

The eye has two main refractive surfaces:

眼睛有兩個主要的折射面：

the cornea and the lens.

角膜和晶狀體

Ideally, these surfaces work together

理想情況下， 這兩個折射面會共同運作

to refract light in a way that accurately focuses light onto the retina,

把光線折射聚焦至視網膜

the layer of light-sensitive tissue at the back of the eye

即眼球後方的一層感光組織

that works with the brain to give rise to vision.

它會與大腦合作，從而產生影像

But many people develop refractive errors,

但很多人發生屈光不正

either during childhood as their eyes are growing,

是在眼睛正成長的孩童時期

or in later life as their eyes age.

或是在眼睛衰退的老年時

Imperfections in the cornea and lens

角膜和晶狀體的缺陷

cause refracted light to be focused in front of or behind the retina,

使得折射光線聚焦在視網膜前面或後面

making images appear blurry.

令影像模糊

People with refractive errors can still see color,

患有屈光不正的人 仍能看見顏色、動作和光

movement,

and light,

but the details of what they're looking at are out of focus.

但他們所見細節是模楜的

People experience refractive errors in different ways,

人們由於眼睛的差異 有不同種類的屈光不正

owing to differences in their eyes.

In some, light refracts too much,

一部分人的眼睛，光線過度折射

and in others, too little.

另一部分人則太少

Eyes with a focal point in front of the retina are called myopic,

焦點落在視網膜前的眼睛稱為「近視」

or short-sighted.

They can see close objects clearly,

他們能清楚看見近處的東西

but those far away are out of focus.

但遠處的則模楜不清

But when the focus point is behind the retina,

但若焦點落在視網膜後的

people are hyperopic, or long-sighted.

這些人則有「遠視」

For them, objects close up are unfocused,

對於他們而言，近處物體模楜不清

but distant objects are crystal clear.

但遠方事物卻清晰可見

Finally, some people have a cornea with a non-spherical shape

最後，有些人的角膜並非呈球面狀

that causes astigmatism,

造成「散光」

a form of out-of-focus vision that makes all objects seem blurred,

是一種不能對焦的視力， 致使無論遠近事物皆模糊不清

whether close or far.

As we age, our eyes face new challenges.

當我們年歲漸長，眼睛面對新挑戰

When we're young, the lens of the eye is flexible

我們年幼時， 眼睛的晶狀體柔韌有彈性

and can change shape to bring images into focus,

能夠改變形狀來把影像聚焦

something called accommodation.

稱為「眼調節」

This keeps objects in focus when we shift our gaze from far to near.

當我們由遠至近轉移目光時， 這使物體影像維持清楚

But as we get older, the lens becomes less flexible,

但當我們漸漸年長，晶狀體的彈性漸減

and can't change shape when we want to look at near objects.

我們想看近物時， 晶狀體未能改變形狀配合

This is called presbyopia,

這稱為「老花」

and it affects adults starting around the age of 40 years.

人從約四十歲開始受它影響

Myopia,

hyperopia,

近視、

遠視、

astigmatism,

散光

and presbyopia.

和老花

Each of these is a refractive error.

每一種都是「屈光不正」

Nowadays we can fix them all with glasses or contact lenses,

現今我們可以透過眼鏡 或隱形眼鏡來矯正它們

which work by refocusing light so it strikes the retina precisely.

原理在於重新聚焦光線， 使其準確落在視網膜上

It's even possible to correct vision with surgery

甚至我們可以透過手術改正視力

using lasers that change the shape of the cornea

利用雷射改變角膜的形狀

and alter its refractive properties.

從而改變它的屈光性

But glasses remain the most popular.

但眼鏡仍是最普及的方法

By using carefully crafted lenses

透過仔細打磨的鏡片

to steer light to exactly the right spot on the retina,

引導光線至視網膜的正確點上

a person's clear vision can be restored.

從而恢復一個人的清晰視力

We've come a long way since Seneca's discovery

自塞內卡的發現和舊時簡陋的眼鏡以來， 我們已有很大的進展

and the crude glasses of yesteryear.

In 1727, a British optician named Edward Scarlett

於1727年，英國光學儀器製造者 愛德華·史嘉歷

developed the modern style of glasses

發展出現代款式的眼鏡

which are kept in place with arms which hook over each ear.

以兩托架掛在兩耳上，以固定位置

Today's glasses take their inspiration from that design,

現今的眼鏡都取材自這設計

but they're also much more precise and personal.

但它們同時更精細和個人化

Each pair is tailored for an individual to bring out their unique powers of sight.

每副眼鏡都為個人度身訂造， 帶出他們獨特的視力

So if you're one of the 500 million people with a problem with close or far vision,

所以如果你是這五億人之一： 有近視或遠視

or both,

或是兩者皆有

there's a pair of glasses out there waiting to reveal a whole new world

總有一副眼鏡等待你， 以展現一個全新的世界 ──

that's hiding in plain view.

一個隱藏在平日視線的世界

翻譯：Crystal Yip